The modern communications era has brought about a tremendous expansion of wireline and wireless networks. Computer networks, television networks, and telephony networks are experiencing an unprecedented technological expansion, fueled by consumer demand. Wireless and mobile networking technologies have addressed related consumer demands, while providing more flexibility and immediacy of information transfer.
Current and future networking technologies continue to facilitate ease of information transfer and convenience to users. Such increased ease of information transfer and convenience to users has recently been accompanied by an increased ability to provide mobile communications at a relatively low cost. Accordingly, mobile communication devices are becoming ubiquitous in the modern world. With the rapid expansion of mobile communications technology, there has been a related rapid expansion in those services that are demanded and provided via mobile communication devices.
Over the history of mobile communications, there have been many different generations of systems developed to enable the use of such communication devices. The first generations of these systems were sometimes developed independently and, at least initially, were not necessarily usable in cooperation with other systems. However, cooperation between communication system developers began to be employed so that new technologies could be enabled to have the potential for synergistic cooperation with other technologies in order to increase overall capacity. Thus, a mobile terminal operable in second generation (for example, 2G) systems such as GSM (Global System for Mobile communications) or IS-95, which replaced the first generation of systems, may in some cases be useable in cooperation with newer generation systems such as third generation systems (for example, 3G) and others that are currently being developed (for example, E-UTRAN (Evolved Universal Terrestrial Radio Access Network)).
The ability of a particular mobile terminal to access multiple systems or communicate via multiple radio access technologies (multi-RATs) is sometimes referred to as “multi-radio access” (MRA). An MRA capable terminal may therefore be enabled to transfer between different RATs (for example, UTRAN (Universal Terrestrial Radio Access Network), E-UTRAN, GERAN (GSM EDGE Radio Access Network), HSPA (High Speed Packet Access)). The goal of such transfers is, of course, to maintain communication continuity through each transfer. The Third Generation Partnership Project (3GPP) has defined various specifications to attempt to standardize aspects of the mechanisms used to achieve this and other goals. One provision of the 3GPP standards provides for handing over of a voice session over E-UTRAN to GERAN as a circuit switched (CS) voice call (e.g., handing over from a packet switched (PS) connection to a CS connection). In other words, for example, SR-VCC provides a mechanism by which to handover from a Voice over Internet Protocol (VoIP) call over a data bearer to a traditional voice call over a CS bearer. However, SR-VCC is also capable of operation in a single RAT environment. For example, a device may be handed over from HSPA to UTRAN where HSPA is part of the UTRAN.
Additionally, other inter-domain handover situations beyond SR-VCC are also possible. One principle or goal for implementation of standards related solutions is to avoid or reduce impacts on a target access network (for example, GERAN). In particular, with respect to SR-VCC from E-UTRAN toward a pre-release 8 target network, it may be desirable to utilize deployed target MSC (mobile switching center) and BSS (base station system) nodes without requiring substantial changes to such nodes to support the SR-VCC solution. However, in some cases, problems may arise due to the fact that the network and the user equipment (UE) being handed over may have different concepts of when a handover has been successfully completed. For example, in each of various different SR-VCC handover scenarios, the UE may consider the handover complete and then send a message indicating as much to the network. The network typically considers the handover complete after receipt of the message sent by the UE. Accordingly, with the difference in handover completion determination conditions established, it is possible for one side to store the new CS key set and the other side to dispose of the new CS key set and instead retain the previously stored CS key set. This scenario may occur, for example, in a handover failure case. More specifically, if the UE provides a transmission (e.g., a handover complete message) that is not received by the network, the UE will store the new CS key set, but the network will retain the old CS key set.
A key set mismatch is normally handled by checking for matching key set identity (KSI (key set identifier) or CKSN (ciphering key sequence number)) in the network and at the UE at a subsequent CS and/or PS connection, where a mismatch triggers a new key exchange (e.g., via authentication and key agreement (AKA)) procedure. A failure may occur when the newly mapped key set has a mapped identity that is the same as an existing stored key set. In particular, for example, if it is not known which of the two possible key sets is stored under the key set identity in the network and at the UE, a mismatch of key sets may be a very serious condition resulting in connection failure or badly ciphered audio. The above listed example is merely one situation where a key mismatch may result following a handover between specific different domains involving SR-VCC. However, it should be appreciated that similar problems related to key mismatches may occur in relation to other inter-domain handovers as well that may not necessarily involve SR-VCC or MRA.
Accordingly, changes to the key handling procedures for inter-domain handovers may be desirable.